The present invention relates to a device, system and method for the secure provision of power to a network device, and in particular, to such a device, system and method in which power is provided while protecting against damage to the network device caused by this power, and/or for preventing unauthorized use of the network by the network device.
Current telephone systems, both analog and digital in a variety of settings, including both home and office use, are highly limited and fixed in functions that they provide. For example, the functionality of such telephones cannot be altered, but rather is limited to the factory-determined features.
In order to increase the flexibility and functionality of such telephony systems, network telephony systems connect a network telephonic device to a server over a packet-switched network such as an IP (Internet Protocol) network, such that these telephony systems may be termed xe2x80x9cIP telephony systemsxe2x80x9d. These telephonic devices can receive data through such a network, and therefore can perform various voice mail and other telephonic functions through software on the connected server over the packet-switched network. Clearly, such a system is more flexible, since additional functions can be provided by adjusting software which resides at the server.
An improved and even more flexible system is disclosed in U.S. Provisional Application No. 60/168,395, filed on Dec. 2, 1999. This network telephony system features a flexible, customizable network telephonic device for receiving and transmitting the telephone calls, such that the telephonic device itself is customizable.
Regardless of the type of network telephonic device and system which is used, all such network telephony systems require a local area network (LAN) for serving a plurality of network telephonic devices. One example of a type of network which is suitable for such a LAN is the Ethernet network. One drawback of network telephony systems, such as those operated over an Ethernet network, is the requirement for a power supply for each network telephonic device. Although each telephonic device could be powered from a local AC power outlet, for example, such a requirement for a local power outlet is clearly disadvantageous. Additionally, if the network telephonic device is to also operate while the main AC power supply is interrupted or discontinued, a separate UPS (uninterrupted power supply) is necessary for each network telephonic device.
In an attempt to overcome such disadvantages, various solutions have been proposed for providing power to the network telephonic devices through the Ethernet or other network cables. Since power is provided through the existing network infrastructure, the requirement for additional cables and/or local power outlets is obviated. With regard to Ethernet networks, the most commonly used cables for Ethernet networks have eight wires, of which four are dedicated to data transmission according to the Ethernet standard: wires 1, 2, 3 and 6. The remaining four wires may preferably be used for power supply.
Alternatively, any of the eight wires of the Ethernet cable may be used for power supply, by multiplexing power and data on the same wire. Such multiplexing techniques are known in the art, and are used for example for regular (analog) telephony systems attached to the PSTN (public switched telephony network), where power and voice signals are carried on a single pair of wires. However, using any of the wires of the Ethernet cable which are unused for data transmission may render the network device vulnerable to power surges. For example, wires 4 and 5 are vulnerable to surges if a network device with an Ethernet socket is accidentally connected to the regular (analog) telephony network. Since the Ethernet socket is larger than the analog telephone plug, such a plug could physically-be inserted into the socket, where it would contact wires 4 and 5 of the Ethernet socket. The analog telephony network delivers relatively high voltage, which might damage the connected network device.
One attempted solution for overcoming this problem was proposed by PowerDSine Ltd. (Israel; http://www.powerdsine.com, as of Jan. 12, 2000), in which the power supply attempts to provide power to the network device which is attached to the Ethernet network, and monitors power consumption by this device to sense if the network device can accept power at such a level. While such a detection mechanism may be implemented for automatic operation, it has the disadvantage that power must initially be supplied to the network device at a sufficiently high level to enable the network device to operate. If, in fact, the device which is attached to the network should not be so connected, then supplying even such a relatively low level of power may prove damaging to the device, the network or both. Additionally, providing power in this controlled manner, while monitoring the consumption of power by the attached network device, does not necessarily comply with the power supply requirements of the network device, in which case the network device would not be able to operate with this supply of power.
Furthermore, such a detection mechanism can only test an attached device for the electrical compatibility with the network, but cannot determine whether the device is authorized to be attached to the network with regard to security. For a network telephonic device, for example, such a lack of security could be potentially problematic, since an unauthorized user could theoretically attach such a device to the network for the purposes of wiretapping or fraud, for example. Thus, clearly this attempted solution has a number of drawbacks.
A more useful solution would provide secure power transmission, both with regard to supplying power without damaging the network and attached devices, and with regard to preventing unauthorized users from attaching a device to the network. This solution would also be useful for network devices other than IP telephones, such as other network appliances for example. Unfortunately, such a solution does not exist.
There is thus a need for, and it would be useful to have, a device, system and method for providing secure power transmission through a computer network such as an Ethernet network, preferably including both the prevention of damage to the network device from the transmission of power and the provision of security for attaching only authorized devices to the network.